81579421440 has 864 divisors, whose sum is σ = 334883727360. Its totient is φ = 18114969600.

The previous prime is 81579421439. The next prime is 81579421447. The reversal of 81579421440 is 4412497518.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81579421447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 74637534 + ... + 74638626.

Almost surely, 2^81579421440 is an apocalyptic number.

81579421440 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81579421440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (167441863680).

81579421440 is an abundant number, since it is smaller than the sum of its proper divisors (253304305920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81579421440 is a wasteful number, since it uses less digits than its factorization.

81579421440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1181 (or 1164 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 81579421440 in words is "eighty-one billion, five hundred seventy-nine million, four hundred twenty-one thousand, four hundred forty".